Recent years have seen development of the biometric authentication technology for determining whether or not to authenticate an individual, by using biometric information such as a fingerprint or a finger vein pattern. The biometric authentication technology is widely used to make a determination on accessibility to a variety of services, such as determination on whether or not to allow room entry/exit, determination on whether or not to allow access to computer, and user authentication in on-line transactions.
For example, when a hand vein pattern is used as biometric information, a biometric authentication apparatus acquires a biometric image representing a vein pattern by a sensor, as an input biometric image. The biometric authentication apparatus determines whether or not input biometric information, which is the vein pattern of a user represented by the input biometric image matches registered biometric information, which is a vein pattern represented by a registered user's biometric image registered in advance. When it is determined that the input biometric information and registered biometric information match, on the basis of a result of the matching process, the biometric authentication apparatus authenticates the user as being an authorized registered user. Then, the biometric authentication apparatus permits the authenticated user to use a host apparatus in which the biometric authentication apparatus is incorporated, or an apparatus connected to the biometric authentication apparatus.
In some cases, the posture of a portion including biometric information with respect to a sensor may differ between the time of registration and the time of matching of biometric information. In such a case, the orientation, the position, and the scale of the biometric information represented on the obtained biometric image may differ between the time of registration and the time of matching. When the orientation, the position, or the scale of the biometric information on the biometric image differ between the time of registration and the time of matching, positions of feature points of the biometric information also differ between the biometric images. This is not preferable due to an increase in the false rejection rate. In view of the above, there have been proposed techniques for reducing a positional deviation of biometric information on a biometric image (see, e.g., PCT International Publication No. 2010/086993, Japanese Laid-open Patent Publication No. 2008-134862, and Japanese Laid-open Patent Publication No. 2010-26658).
For example, the authentication apparatus disclosed in PCT International Publication No. 2010/086993 calculates the difference in the position of a body part relative to an imaging apparatus at the time of registration and matching, and outputs guidance information to prompt the user to reduce the difference.
The vein authentication apparatus disclosed in Japanese Laid-open Patent Publication No. 2008-134862 captures a finger knuckle print image on the pad side of a finger, and calculates a positional deviation of the placed finger from the finger knuckle print image and a distance value representing the deviation for correcting the position of a vein image.
The palm position detecting apparatus disclosed in Japanese Laid-open Patent Publication No. 2010-26658 detects the horizontal direction of the palm in the image, and rotates the image on the basis of the horizontal direction for detecting the coordinates of the upper, lower, left, and right ends of the palm.